Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Peel and dice the sweet potato and carrots into uniform 1-inch cubes to ensure even roasting.
Mince the garlic cloves and finely chop the fresh rosemary leaves, discarding the woody stems.
In a medium bowl, toss the diced vegetables with half of the olive oil, half of the sea salt, and half of the black pepper.
Pat the chicken breast dry with a paper towel and rub with the remaining olive oil, minced garlic, chopped rosemary, and remaining salt and pepper.
Arrange the chicken and vegetables in a single layer on the prepared baking sheet, ensuring they are not overcrowded.
Roast for 25 to 30 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are fork-tender and slightly browned.
Let the chicken rest for 5 minutes before slicing to keep it juicy, then serve alongside the roasted root vegetables.